1. Field of the Invention
The present invention relates to a motorized roller such as a motor pulley or a motor roller used in a conveyor or the like, and more particularly to a cooling structure for a motorized roller that has a simple construction, and is capable of effectively reducing temperature increases inside the apparatus.
2. Description of the Related Art
Motorized rollers have been proposed in a variety of configurations (for example, see Japanese Patent Laid-Open Publication No. 1999-127556). The proposed motorized roller is configured in such a manner that a motor and a reducer are disposed inside a roller body, and the rotation of the motor is reduced by the reducer and then transmitted to the roller body so that when fixed to an external member the roller body is able to rotate. As shown in FIG. 4, this type of motorized roller can be used as a motor roller MR for moving a package 4 placed on top of a conveyor 2 through direct contact. Alternatively, as shown in FIG. 5, the motorized roller can also be used as a motor pulley MP for moving the package 4 via a belt 6.
FIG. 6 shows an example of a conventional motorized roller MR1.
A motor M1 and a reducer R1 are housed inside a pipe body (a drum) 10, and the rotation of the motor M1 is reduced by the reducer R1 and then transmitted to the pipe body 10.
The motor M1 is equipped with a motor shaft 12, and this motor shaft 12 also functions as the input shaft 13 for the reducer R1.
The reducer R1 is a so-called oscillating inner gearing planetary gear reducer comprising the input shaft (a first shaft) 13, an external gear 16, an internal gear 18, and an output shaft (a second shaft) 20. The external gear 16 is incorporated into the outer periphery of the input shaft 13 via an eccentric body 14 and is able to undergo eccentric oscillating rotation relative to the input shaft 13. The internal gear 18 engages on the inside with the external gear 16. The output shaft 20 is connected to the external gear 16 so that the output shaft 20 can absorb the eccentric oscillation component of the external gear 16.
When the input shaft 13 undergoes a single rotation, the external gear 16 undergoes a single eccentric oscillation about the motor shaft 12 via the eccentric body 14. This eccentric oscillation causes a sequential displacement in the (internal contact) engagement position between the internal gear 18 and the external gear 16, so that the engagement position makes a single rotation. However, because the number of teeth of the external gear 16 is less than the number of teeth of the internal gear 18 by a value of N (usually 1), the external gear 16 undergoes a phase displacement (rotation) relative to the internal gear 18 by an amount equivalent to this difference N in the number of teeth.
Accordingly, if only this rotation component of the external gear 16 is delivered, then a large speed reduction ratio of (difference in the number of teeth N)/(number of teeth of the external gear) can be achieved. In the conventional example shown, the oscillation component of the external gear 16 is absorbed by the loose fit between an inner pin 22 that protrudes from the output shaft (the second shaft) 20, and an inner pin aperture 24 that penetrates into the external gear 16. Only the rotation component is then transmitted to the output shaft (the second shaft) 20 via the inner pin 22.
The rotational torque transmitted to the output shaft 20 is transmitted to the pipe body 10 via a bracket 26.
However, in this conventional motor roller MR1, the torque generated on the motor shaft 12 side, which corresponds to the reactive torque for rotating the pipe body 10, is transmitted to a fixed shaft 38, and the reactive torque generated on the internal gear 18 side is transmitted to the same fixed shaft 38 via a casing 30, a mounting plate 32, a fixed pipe 34, and a bolt 36. As a result, a fixed pipe 34 is positioned inside the pipe body 10 to form a double pipe arrangement. This means that size increases (particularly in the radial direction) are unavoidable, and that the number of components increases.
One technique that has been proposed for resolving these types of problems is the motorized roller MR2 shown in FIG. 7. FIG. 7 is a side sectional view of the motorized roller MR2.
A reducer R2 employed in this motorized roller MR2 is similar to the first conventional example described above in that it represents an oscillating inner gearing planetary gear reducer, and comprises an input shaft (a first shaft) 53 that forms a single integrated unit with the motor shaft 52 of the motor M2, an eccentric body 54, an external gear 56, and an internal gear 58. An output shaft (a second shaft) 62 is connected to the external gear 56 via an oscillating shaft 60 that absorbs the eccentric oscillation component of the external gear 56.
In this motorized roller MR2, a reaction force to the driving force of the roller body 50 exists as either a torque that rotates the internal gear 58, or as a torque that rotates the motor shaft 52 reversely. Reactive torques generated at the internal gear 58 and the motor shaft 52 are transmitted to a mounting shaft 72 via the casing 70 that houses the motor M2 and the reducer R2. The reactive torques are received by fixing the mounting shaft 72 to an external member 80 such as a conveyor frame or the like so that rotation is prevented.
Accordingly, in the motorized roller MR2 there is no need to adopt a double pipe structure inside the roller body 50, meaning the apparatus can be made more compact (particularly in the radial direction).
However, as a result of making the conventional motorized roller MR2 more compact in the radial direction, the spacing S1 between the roller body 50 and the casing 70 decreases, and because one end 70a of the casing 70 is closed, heat generated by the motor M2 and the reducer R2 tends to become trapped inside the motorized roller MR2, meaning the inside is prone to increase in temperature. Moreover, because the roller body 50 rotates around the casing 70, which is fixed to the external member 80, the air between the casing 70 and the roller body 50 also moves in a circumferential direction in conjunction with the rotation of the roller body 50. Considered from a different perspective, the air between the casing 70 and the roller body 50 is hard to move in the axial direction, so that the same air remains trapped, making it difficult to dissipate the heat generated within the roller.
Furthermore, introducing an oil coolant into the motorized roller MR2 could be considered as one method of achieving cooling, but this would require measures to prevent problems such as oil leakage, and would not only make the structure more complex, but would also increase the number of structural restrictions in designing.